The polls show Labor's vote sliding week by week. The Coalition is cruising to victory, probably with a substantial majority in the lower house. But what of the Senate?

This will be a Senate election like no other. There will be 529 candidates standing for just 40 Senate seats. Victoria has 97 candidates running in 39 party tickets. NSW has 110, Queensland 82, Western Australia 62, South Australia 73, Tasmania 54, the ACT 27 and even the Northern Territory has 24.

Anything is possible. The votes will be dispersed so widely that an upset result is possible, as we had in 2004 in Victoria, when Family First's Steve Fielding won a seat with just 1.9 per cent of the vote, or in 2010, when the DLP's John Madigan won with just 2.3 per cent.

Six senators are elected from each state, to six-year terms, so the 36 senators elected in 2010 will remain in the new Parliament, with a 19-17 split in favour of the left: 13 Labor and six Greens against 16 Coalition and Madigan.

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To win power in its own right, the Coalition must win not only three of the six seats in each state and one in each territory, but a fourth seat in three states. That is unlikely, but a combination of right-of-centre parties could win a majority in the new Senate, enabling it to pass its key legislation.

In Victoria, while Julian Assange is standing for WikiLeaks, and Fiona Patten of the Sex Party and David Collyer of the Democrats won good preference deals, it's more likely the state will vote in three Coalition senators, two Labor and one Green – with the Greens' Janet Rice taking the seat Labor's David Feeney gave up for Batman.

Assange scored badly on preferences, and cannot leave the Ecuadorian embassy in London to take up his seat if he wins. Last week he said his running mate, columnist Leslie Cannold, could take up the seat – but for that to happen, he would have to resign it first. If so, why vote for him?

NSW could provide the biggest boilover. Preference deals have worked well for One Nation chief Pauline Hanson, who has her best chance since 1998 of returning to Federal Parliament.

Minor parties such as the Reverend Fred Nile's Christian Democrats, the Shooters, the DLP, the Liberal Democrats and Katter's Australian Party have all placed her high on their tickets. If she can pull in 5 per cent of the vote, as she did in 2004 in Queensland, she could take the final seat from Labor and the Greens.

Ray Brown of the Building Australia Party also has a chance. He won just 0.25 per cent last time, but with lots of second or third preferences, and high preferences from 27 of the 42 tickets submitted, he could break the record for the lowest vote for a winning candidate.

The likely result is that NSW will split three-all between left and right, with the Coalition retaining three seats, while Greens state MP Cate Faehrmann could unseat Labor senator Ursula Stephens.

Queensland is home to Bob Katter and Clive Palmer, and they swapped preferences between their celebrity candidates: country singer James Blundell, for Katter, and rugby league legend Glenn Lazarus, known on the field as "the brick with eyes", for Palmer.

Queensland is where the Coalition is most at risk of winning only two seats, maybe losing one to Blundell or Lazarus. Rudd's home-state support would have to collapse to stop Labor and the Greens winning three between them.

One of the oddest calls is South Australian independent Nick Xenophon's decision to split his preferences between Liberals and Labor. Xenophon has an impact in the Senate only if he holds the balance of power, which his preferences will make less likely.

They put third-placed Liberal Cathie Webb in pole position to unseat Greens senator Sarah Hanson-Young, and head off Family First's Bob Day, who almost won in 2010.

Last time Xenophon split his preferences between the two smaller parties. This time South Australia will probably end up Coalition three, Labor two, plus Xenophon.

Western Australia is the Coalition's best chance of winning four seats. While WA has always voted 3-2-1 in Senate elections, this time the Nationals' lead candidate will be former West Coast star David Wirrpanda (with a running mate named Eagles).

Wirrpanda has attracted some unlikely preferences, including from WikiLeaks, and could unseat the Greens to give the Coalition two Aboriginal members from the West.

Tasmania is now in recession, and the Liberals look set to reclaim the Senate seat they lost to Labor in 2007, returning Tasmania to a 3-2-1 split.

The Northern Territory and the ACT seats have always split one-all in the past. But the Liberals' ACT seat is never safe, and the Greens' Simon Sheikh, former director of GetUp!, will get almost all the preferences, even from Katter's and Palmer's parties. A Greens win is unlikely, but not impossible.

The Coalition's chances of a Senate majority are remote. Its chances of getting a Senate it can work with are strengthening.